1. Field of the Invention
The present invention relates to apparatus and methods for restraining the heart. More particularly, the invention relates to apparatus and methods for accessing the pericardium and at least partially enclosing the heart with a cardiac restraint apparatus.
2. Description of the Related Art
The present invention is generally directed to apparatus and methods for restraint of the cardiac wall. The invention is particularly suited for the treatment of cardiac diseases which result in atrial or ventricular dilation. The invention includes minimally invasive methods to access the heart and restrain the cardiac wall, resulting in the prevention or reduction of cardiac dilation in patients known to have experienced such dilation or who have a predisposition for such dilation occurring in the future. A cardiac restraint apparatus according to the present invention is typically applied to the epicardial surface of the heart, such that the cardiac restraint apparatus at least partially encloses the heart.
Cardiac dilation occurs with different forms of cardiac disease, including congestive heart disease, post-myocardial infarctions, and dilated cardiomyopathy. In certain instances, congestive heart disease may result from viral infections. In such cases, the heart may enlarge to such an extent that the adverse consequences of heart enlargement continue after the viral infection has passed and the disease continues its progressively debilitating course. In some cases, such as post-myocardial infarction, the dilation may be localized to only a portion of the heart. In other cases, such as hypertrophic cardiomyopathy, there is typically increased resistance to filling of the left ventricle with concomitant dilation of the left atria. In dilated cardiomyopathy, the dilation is typically of the left ventricle with resultant failure of the heart as a pump. In advanced cases, dilated cardiomyopathy involves the majority of the heart. Causes of congestive heart disease are not fully known.
As the heart enlarges, the heart is performing an increasing amount of work in order to pump blood during each heart beat. In time, the heart becomes so enlarged that the heart cannot adequately supply blood. An afflicted patient is fatigued, unable to perform even simple exerting tasks and experiences pain and discomfort. Further, as the heart enlarges, the internal heart valves cannot adequately close. This impairs the function of the valves and further reduces the heart""s ability to supply blood. With each type of cardiac dilation, there are associated problems ranging from arrhythmias which arise due to the stretch of myocardial cells, to leakage of the cardiac valves due to enlargement of the valvular annulus.
Drugs are sometimes employed to assist in treating problems associated with cardiac dilation. For example, Digoxin increases the contractility of the cardiac muscle and thereby causes enhanced emptying of the dilated cardiac chambers. On the other hand, some drugs, for example, beta-blocking drugs, decrease the contractility of the heart and thus increase the likelihood of dilation. Other drugs including angiotensin-converting enzyme inhibitors such as Enalopril, which help to reduce the tendency of the heart to dilate under the increased diastolic pressure experienced when the contractility of the heart muscle decreases. Many of these drugs, however, have side effects which make them undesirable for long-term use.
Apparatus to prevent or reduce dilation and thereby reduce the consequences of dilation have also been described. Patches made from low porosity materials, for example Dacron(trademark), have been used to support the cardiac wall. Other apparatus are found in U.S. Pat. No. 4,957,477 to Lundback dated Sep. 18, 1990; U.S. Pat. No. 5,131,905 to Grooters dated Jul. 21, 1992; U.S. Pat. No. 5,150,706 to Cox et al. dated Sep. 29, 1992; U.S. Pat. No. 5,143,082 to Kindberg et al dated Sep. 1, 1992; U.S. Pat. No. 5,256,132 to Snyders dated Oct. 26, 1993; U.S. Pat. No. 5,702,343 to Alferness dated Dec. 30, 1997; U.S. Pat. No. 6,077,218 to Alferness dated Jun. 20, 2000; U.S. Pat. No. 6,085,754 to Alferness dated Jul. 11, 2000; and U.S. Pat. No. 6,095,968 to Snyders dated Aug. 1, 2000.
The ""477 patent teaches a double-walled jacket surrounding the heart. A fluid fills a chamber between the walls of the jacket. The inner wall is positioned against the heart and is pliable to move with the heart. Movement of the heart during beating displaces fluid within the jacket chamber. The ""706 patent discloses a medical apparatus for enclosing an internal body organ, comprising a filamentary strand with noose and free end portions and a surgical bag with an opening. The ""082 patent discloses a cooling net for cardiac or transplant surgery, comprising a porous net that is fitted and secured around the organ. Both of the ""905 and ""132 patents teach cardiac assist apparatus which pump fluid into chambers opposing the heart to assist systolic contractions of the heart. The ""343 and ""218 patents teach an adjustable jacket to constrain cardiac expansion during diastole. The ""754 patent discloses a biologically compatible jacket adapted to be secured to the heart. The ""968 patent discloses a viscous cardioplasty jacket for buttressing the ventricular heart walls.
None of these apparatus include a sheath to facilitate endoscopic introduction of the apparatus, or guide elements for positioning the cardiac restraint apparatus around the heart. Moreover, none of these apparatus include hollow guide tubes that permit an instrument to be advanced through their lumens to engage the mouth of the jacket and secure the mouth of the jacket to the pericardium. Furthermore, none of these references teach the introduction of a cardiac restraint apparatus via a single subxiphoid incision. Accordingly, there is a need for an improved cardiac restraint apparatus that can be more easily introduced via a minimally invasive approach, and improved minimally invasive methods for introducing cardiac restraint apparatus.
The invention is a method and apparatus for accessing the heart within the pericardium and restraining the heart by at least partially enclosing the heart with a cardiac restraint apparatus.
One embodiment of a cardiac restraint apparatus according to the invention comprises a jacket, the jacket having a rim which defines an opening for receiving a heart. The apparatus also comprises a knot pusher that has a hollow elongate body, and a strand that extends around the rim of the jacket and is tied into a slipknot. The strand is positioned such that at least one end portion of the strand extends through the knot pusher such that a distal end of the knot pusher can be moved into engagement with the slipknot, whereby pulling the end portion of the strand away from the heart while pushing the knot pusher against the slipknot and reducing the diameter of the opening defined by the rim. In addition, the apparatus comprises one or more guide elements that are attached to the jacket.
In another embodiment of a cardiac restraint apparatus according to the invention, the jacket is folded to reduce the profile of the apparatus. Optionally, the folded jacket is enclosed by a sheath. One embodiment of such a sheath includes a generally cylindrical body having a proximal end and a distal end, and also includes perforations along the sheath body such that the sheath can be removed from the apparatus by tearing the sheath body along the perforations. Optionally, a pull tab is attached to the proximal end of the sheath body. By pulling the pull tab away from the jacket, the surgeon can tear the sheath along the perforations and remove the torn sheath from the patient.
In one embodiment of a cardiac restraint apparatus according to the invention, the strand extending around the rim of the jacket is a suture strand, for example a nylon suture strand.
In a class of embodiments the guide elements are one or more guide tubes removably attached to the rim of the jacket. In some of these embodiments, the guide tubes are hollow. In some of the embodiments, at least one of the guide tubes defines a lumen dimensioned to receive a surgical instrument, for example a tacking instrument. In other embodiments, the guide elements are one or more handles, for example handles composed of suture strands, attached to the rim of the jacket.
In another class of embodiments, the apparatus comprises at least one elastic band having a first portion terminating at a first end and a second portion terminating at a second end, with the first portion and the second portion of the elastic band being joined together at a location between the first end and the second end. The apparatus also includes a sheath, which includes a generally cylindrical body having a proximal end and a distal end. The sheath body may also define perforations, preferably longitudinally positioned perforations, such that the sheath can be removed from the apparatus by tearing the body along the perforations. The sheath can also include a pull tab that is attached to the proximal end of the sheath body, for pulling the sheath away from the apparatus by pulling the pull tab away from the jacket.
In some such embodiments, the elastic band includes calibrated markings for calibrating the tension of the elastic band. In other embodiments, the first and second ends of the elastic band are configured to be engaged by a grasping instrument.
Another aspect of the invention is a method of enclosing the heart with any embodiment of the inventive cardiac restraint apparatus. In one embodiment, the invention is a method of at least partially enclosing a heart with a cardiac restraint apparatus that includes a jacket. The method comprises the steps of: a) making a surgical incision to provide an entry point for the cardiac restraint apparatus; b) introducing a cutting tool through the incision and using the cutting tool to make an opening in the pericardium through which the cardiac restraint apparatus can be advanced into engagement with the heart; c) advancing the cardiac restraint apparatus through the incision and the opening into engagement with the heart; and d) sweeping the jacket along the heart to at least partially enclose the heart in the jacket. The surgical incision can be a subxiphoid incision, a trans-xiphoid incision, a thorascopic incision or another incision.
An alternative embodiment of the inventive method includes the steps of: a) making a surgical incision to provide an entry point for an endoscopic cannula; b) inserting the endoscopic cannula into the surgical incision, wherein the endoscopic cannula has at least one access port; c) advancing the endoscopic cannula to the pericardium under endoscopic visualization; d) introducing a cutting tool into the access port of the endoscopic cannula; e) making an opening in the pericardium using the cutting tool, through which the cardiac restraint apparatus can be advanced into engagement with the heart; f) advancing the endoscopic cannula into the pericardium through the opening; g) advancing the cardiac restraint apparatus into at least one access port of the endoscopic cannula into engagement with the heart; h) sweeping the jacket along the heart to at least partially enclose the heart in the jacket.
Another embodiment of a method according to the invention uses the embodiment of the cardiac restraint apparatus that includes a jacket and one or more guide tubes. In this method, the step of enclosing the heart with the cardiac restraint apparatus includes the steps of: a) advancing a tacking instrument into at least one access port of the endoscopic cannula to access the pericardium; b) tacking the rim of the jacket to the posterior pericardium using the tacking instrument; and c) manipulating the guide tubes of the cardiac restraint instrument to sweep the jacket over the anterior aspect of the heart thereby at least partially enclosing the heart with the jacket. The jacket is then tightened around the heart by reducing the diameter of the opening of the jacket by pulling the end portion of the strand away from the heart while pushing the knot pusher against the slipknot.
Another embodiment of a method according to the invention uses the embodiment of the cardiac restraint apparatus that includes a jacket and one or more handles. In this method, the step of enclosing the heart with the cardiac restraint apparatus includes the steps of: a) advancing one or more guide strands into at least one access port of the endoscopic cannula, the one or more guide strands having a sufficient length to enable the proximal ends of the one or more guide strands to be grasped outside the body when the distal ends of the guide strands are positioned near the heart; b) advancing a tacking instrument into at least one access port of the endoscopic cannula; c) tacking the one or more guide strands to the posterior pericardium using the tacking instrument; d) passing the one or more guide strands through the one or more handles on the rim; and e) using the guide strands to manipulate the jacket, thereby at least partially enclosing the heart with the jacket.
Another embodiment of a method of restraining the heart with a cardiac restraint apparatus involves a cardiac restraint apparatus that includes an elastic band. The method comprises the steps of: a) making a surgical incision to provide an entry point for the cardiac restraint apparatus; b) introducing a cutting tool through the incision and using the cutting tool to make an opening in the pericardium through which the cardiac restraint apparatus can be advanced into engagement with the heart; c) advancing the cardiac restraint apparatus through the incision and the opening into engagement with the heart; and d) restraining the heart with the elastic band by securing the elastic band around the heart. This method includes methods in which the surgical incision is a subxiphoid incision, a trans-xiphoid incision, and a thorascopic incision.
An alternative embodiment of this method includes the steps of: a) making a surgical incision to provide an entry point for an endoscopic cannula; b) inserting the endoscopic cannula into the surgical incision, wherein the endoscopic cannula has at least one access port; c) advancing the endoscopic cannula to the pericardium under endoscopic visualization; d) introducing a cutting tool into the access port of the endoscopic cannula; e) making an opening in the pericardium using the cutting tool, through which the cardiac restraint apparatus can be advanced into engagement with the heart; f) advancing the endoscopic cannula into the pericardium through the opening; g) advancing the cardiac restraint apparatus into at least one access port of the endoscopic cannula into engagement with the heart; and h) restraining the heart with the elastic band by securing the elastic band around the heart.
In the methods using the cardiac restraint apparatus that includes at least one elastic band, in one embodiment the step of restraining the heart with the cardiac restraint apparatus can include the steps of: a) advancing a tacking instrument into the opening in the pericardium (or, in the minimally invasive methods, into the access port of the endoscopic cannula to access the pericardium); b) tacking the elastic band to the posterior pericardium at a point between the first end and the second end; c) grasping the first portion, moving the first portion to the anterior aspect of the heart, and tacking the first portion to the pericardium overlying the anterior aspect of the heart; d) grasping the second portion, moving the second portion over the anterior aspect of the heart, and tacking the second portion to the pericardium overlying the anterior aspect of the heart; and e) attaching (preferably by tacking or clipping) the first and second portions together (preferably at a location overlying the anterior aspect of the heart) to provide a calibrated tension on the heart. The steps of grasping the first and second portions of the elastic band may be performed with any of a variety of grasping tools, for example a clip applier.